Irreversibility Distribution Research Articles

Numerical simulations of irreversibility for nonlinearly radiative and chemically reactive flow of Maxwell fluid

The cooling & heating phenomena are involved in numerous engineering-industrial operations and have become essential for the development of thermal electronic & energy devices. In this paper, study is performed on entropy production with an emphasis on nonlinearized thermal radiation and viscous dissipation under the consequence of time dependent magnetic field for an unsteady flow of chemically reactive Maxwell fluid in Darcian porous media. The flow governing equations are solved numerically in MATLAB (bvp4c). Graphs are plotted demonstrating the distribution of irreversibility and entropy generation. Numerical results of the impressions of material parameters on Skin friction, Nusselt and Sherwood numbers are also tabulated. This study establishes that the efficiency of thermal devices can be upgraded by higher order chemical reaction and viscous dissipation effects together with the compressed nonlinear radiation and magnetic effects. Also, unsteadiness in the flow, porosity and magnetic effects enhance the shearing stress on the surface leading to greater surface friction while solar radiation and surface heating due to nonlinearity in radiative force favour the heat transferable rate leading to an improvement in convection rate. These inferences can be helpful in the development of proper thermal electronic and industrial devices with solar radiation applications.

A novel exergy analysis method for cerium-based solar thermochemical cycles

Ce-based thermochemical cycles are characterized by high stability and adaptability to operating temperatures. But few studies have been conducted in terms of exergy prospect. In this study, we propose an exergy analysis model and identify its irreversibility distribution. Through introducing an Energy Level-Enthalpy Change (A-∆H) diagram, we capture this distribution and reveal the trend of irreversibility variation. The results show that irreversibility occurs mainly in heat exchangers and reduction reactors and is influenced by temperature and pressure. Previous studies have focused only on the operating parameters, but this has led to negligible improvement in efficiency, hence the need for a comprehensive analysis using sound mathematical methods. We improve the exergy efficiency by 177% through theoretically optimizing the operating conditions and detail the reasons for the reduction in exergy losses. This study provides theoretical guidance and analytical tools for experiments.

Thermodynamic optimization of heat exchanger circuitry via genetic programming

In this study, an evolutionary thermodynamic technique was developed for the optimization of heat exchanger circuitry. The proposed technique is capable of handling the unrestrained implementation of genetic operators while ensuring circuitry feasibility and basic manufacturability. The optimization tool was used to clarify the optimal heat transfer features in relation to the characteristics of the refrigerant and to provide a thermodynamic interpretation of the optimization results to extract general design guidelines. Evaporator circuitry optimization was conducted under given cooling capacity, superheating degree, and boundary conditions representative of air-conditioning applications. The consistency between the minimum entropy generation and the maximum coefficient of performance (COP) was demonstrated under these settings. Accordingly, heat exchanger configurations that take maximum advantage of the thermodynamic benefits of each refrigerant are proposed by optimizing the distribution of friction and heat transfer irreversibility. Consequently, the evaporator outlet pressure increases, thus lowering the compression ratio and maximizing the COP. The developed optimization method maximizes the benefits of low-GWP alternative refrigerants and shows that zeotropic mixtures may exhibit performance analogous to that of R32 and higher than that of R410A by approaching a Lorenz cycle operation.

Hydrothermal and entropy generation performance of convergent tubes with various dimple shapes

This paper introduces a comprehensive study on the hydrothermal and entropy generation performance of convergent tubes designed with different dimple shapes. The effects of the dimple shape on the flow characteristics (heat transfer and friction) are investigated using validated computational fluid dynamics (CFD) numerical modelling and simulation tools. Inside convergent tubes with different dimple designs, turbulent flows are subjected to a continuous heat flux of 40 kW/m2. Dimpled tube geometries of different diameter ratios (DR) were built within ANSYS-Fluent software (V2022 R2). Four different dimple shapes were investigated: (a) spherical, (b) cylindrical, (c) conical, and (d) stepped-conical. These dimple shapes were examined to investigate the optimal configuration with the best hydrothermal and entropy generation performance. A comparison is made against the baseline straight smooth tube case. The main performance indicators for comparison are Nusselt number (Nu), friction factor (f), and thermal enhancement factor (TEF), calculated for different Reynolds numbers, Re = 3000 to 40,000, and at different diameter ratios, DR = 1 to 2. In addition, thermal, viscous, and total entropy components, the Bejan number (Be), the enhanced entropy generation ratio (Ns,en), and the irreversibility distribution ratio (φs) are evaluated based on the selected geometrical configurations. The results showed that the dimple shape significantly affects the hydrothermal and entropy generation characteristics of convergent tubes. The best average value of the TEF was attained by convergent tubes with stepped-conical dimple shapes at DR = 1.75, which represents a 7.81% increase over the reference smooth tube (the maximum TEF value is 1.3243 at Re = 3000 and DR = 1.25). Furthermore, the minimum levels of Ns,en were achieved by tubes with stepped-conical dimples, with average reductions of 36.92% over the studied Re range. The study provides valuable insights into the design and optimization of convergent tubes with various dimple shapes for various applications.

Effects of nonlinear thermal radiation on magnetized - nanofluid flow through an inclined microporous channel: An investigation of second law analysis.

This study aimed at studying the variational effect of nonlinear thermal radiation on the flow of Casson nanofluid ( ) through a porous microchannel with entropy generation. The novelty of this investigation includes the incorporation of porous media, nonlinear radiative heat flux, and convective heat transfer at the channel interface into the energy equation, which results in an enhanced analysis for the cooling design and heat transfer of microdevices that utilize nanofluid flow. Particularly, alumina ( ) is considered as the nanoparticles in this blood base fluid due to associated advanced pharmaceutical applications. With dimensionless variables being utilized, the governing equationsare minimized to their simplest form. The Chebysev-based collocation technique was employed to numerically solve the resultant ordinary differential equations with the associated boundary conditions and the impact of flow, thermal, and irreversibility distribution fields are determined through graphs. The findings identified that higher levels of Hartmann number produce the Lorentz force, which limits fluid flow and lowers velocity, the response of nonlinear thermal radiation diminishes the heat transfer rate, and a rise in the Casson parameter also reduces the Bejan number. The results of this research can be used to improve heat transfer performance in biomedical devices, design-efficient energy conversion cycles, optimize cooling systems, and cover a wide range of energy technologies from renewable energy to aerospacepropulsion.

Research on storage stability differences between ceftriaxone sodium products

The conditions and mechanisms leading to stability differences between ceftriaxone sodium products were examined to ensure drug quality and efficacy. We used a combination of powder X-ray diffraction and thermogravimetric analysis to examine the differences between preparations for injection from different pharmaceutical processes to elucidate the changed processes by exposing samples to different humidity and high-temperature conditions. Water loss or absorption due to varying environmental humidity levels did not adversely affect the crystal structure, but could lead to the reversible redistribution of hepta-hydrate in the unit cell of generic products, causing its stability change. The irreversible distribution of hydrate may occur when generic drugs stored at 25 °C, whereas the brand-name products remained stable at 40 °C. Therefore, generic ceftriaxone sodium and its powder preparations would be acceptable by better controlled sealing and storing under cool conditions during storage period to meet the efficacy and stability.

4E analyses of a novel solar-assisted vapor injection autocascade high-temperature heat pump based on genetic algorithm

Insufficient heating performance is one of the main obstacles that inhibit the widespread application of autocascade heat pump. Therefore, a novel solar-assisted vapor injection autocascade high-temperature heat pump is put forward, which owns two working modes to take full use of solar energy and air energy. At first, the performance variations of the novel system with key operating parameters are theoretically investigated to assess the system characteristics. Thereinto, under considered condition, SV mode is more appropriate to the novel system than VA mode under over 200 W m−2 solar radiation intensity. And then, the energy, exergy, economic and environmental performance of the novel system, vapor injection autocascade heat pump and convenient autocascade heat pump is conducted based on genetic algorithm. The novel system respectively increases the maximum heating COP and corresponding heating capacity by averages of 16.5 % and 18.1 %, in comparison with the vapor injection autocascade heat pump. The irreversibility distributions in three systems are also analyzed. Moreover, the novel system produces the lowest full life cycle cost and air pollutant emissions among three systems. Under given application scenario, the payback period is 2.06 years and 2.95 years when the novel system is adopted to replace other two systems.

Effect of solid obstacle and thermal conditions on convective flow and entropy generation of nanofluid filled in a cylindrical chamber

PurposeOne of the major challenges in the design of thermal equipment is to minimize the entropy production and enhance the thermal dissipation rate for improving energy efficiency of the devices. In several industrial applications, the structure of thermal device is cylindrical shape. In this regard, this paper aims to explore the impact of isothermal cylindrical solid block on nanofluid (Ag – H2O) convective flow and entropy generation in a cylindrical annular chamber subjected to different thermal conditions. Furthermore, the present study also addresses the structural impact of cylindrical solid block placed at the center of annular domain.Design/methodology/approachThe alternating direction implicit and successive over relaxation techniques are used in the current investigation to solve the coupled partial differential equations. Furthermore, estimation of average Nusselt number and total entropy generation involves integration and is achieved by Simpson and Trapezoidal’s rules, respectively. Mesh independence checks have been carried out to ensure the accuracy of numerical results.FindingsComputations have been performed to analyze the simultaneous multiple influences, such as different thermal conditions, size and aspect ratio of the hot obstacle, Rayleigh number and nanoparticle shape on buoyancy-driven nanoliquid movement, heat dissipation, irreversibility distribution, cup-mixing temperature and performance evaluation criteria in an annular chamber. The computational results reveal that the nanoparticle shape and obstacle size produce conducive situation for increasing system’s thermal efficiency. Furthermore, utilization of nonspherical shaped nanoparticles enhances the heat transfer rate with minimum entropy generation in the enclosure. Also, greater performance evaluation criteria has been noticed for larger obstacle for both uniform and nonuniform heating.Research limitations/implicationsThe current numerical investigation can be extended to further explore the thermal performance with different positions of solid obstacle, inclination angles, by applying Lorentz force, internal heat generation and so on numerically or experimentally.Originality/valueA pioneering numerical investigation on the structural influence of hot solid block on the convective nanofluid flow, energy transport and entropy production in an annular space has been analyzed. The results in the present study are novel, related to various modern industrial applications. These results could be used as a firsthand information for the design engineers to obtain highly efficient thermal systems.

Optimization of entropy generation and thermal mechanism of MHD hybrid nanoliquid flow in a sinusoidally heated porous cylindrical chamber

The present computational investigation explores the fluid and thermal characteristics along with entropy generation due to buoyancy-driven magnetohydrodynamic (MHD) convective flow of aqueous hybrid nanoliquid filled in a nonuniformly heated porous cylindrical chamber. The fluid motion in the enclosure is modeled by Brinkman — extended Darcy model. The modeled equations are resolved by finite difference approach. The computations are conducted for Rayleigh number (103–105), Hartmann number (0–50), Darcy number (10−5–10−1), different nanoparticle shapes and nanoparticle volume fraction (Ag/MgO: 0–0.05) to understand the characteristic of flow, thermal and irreversibility distribution. With vast numerical simulations, the outcomes reveal that though the buoyancy force is greater, the fluidity cannot be enhanced unless the permeability and magnetic field strength are optimally maintained. As Ra,Ha and Da is varied respectively from 103 to 105, 50 to 0 and 10−5 to 10−1, the fluidity has been enhanced by 99.39%,83.26% and 99.79%. Among all considered parametric combinations, it has been noticed that the choice of Ha=0,Ra=105,Da=10−1 with proper ratio of nanoparticles enhance the system efficiency. However, minimal entropy generation can be achieved with greater Hartmann and lower Darcy numbers. Furthermore, it has been found that blade shaped nanoparticles lead to increase the performance of thermal system.

Irreversibility Distribution Ratio Used in Entropy Generation Equation for Convective Flows Re-visited

The present numerical investigation describes a new consistent and accurate approach to the square cavity benchmark problems for computing entropy generation during natural or mixed convection flows. This new approach differs from the classic one in that the irreversibility distribution ratio in the dimensionless entropy generation equation is no longer arbitrarily chosen, as reported in the majority of previous research works, which is a very serious violation of the scientific rules but is precisely calculated. Indeed, the computation of the exact value of the irreversibility distribution ratio is based on two indispensable features. One concerns the thermophysical properties of the working fluid at a fixed Prandtl number or at a given reference temperature and the other concerns a reference length of the geometrical configuration considered, depending on the Rayleigh number. Comparing results indicates that the irreversibility distribution ratio, more frequently used by a significant number of researchers, is usually vastly overestimated which will involve an increase in entropy generation and, consequently, an expensive oversizing in all real processes involving flowing fluids.

Comparative study of entropy distribution for generalized fluid between an inclined channel in the perspective of classical and non-Fourier’s law

The key challenge in the design of thermal appliances is to degrade entropy production with maximal energy dissipation to improve system efficiency in a variety of engineering applications, such as nozzle design,converging die, and rocket design. Due to the existence of both tangential and radial components, which have a significant impact on the fluid movement, coupled transport rates, and entropy development in an inclined channel presents a greater challenge. The current inquiry intended to address the combined impacts of Cattaneo-Christove (C-C) heat flux and classical theory on thermal dissipation, along with irreversibility distribution in a tilted porous media. The Carreau nanofluid confined between two finite intersecting plates in the presence of a porous Darcy-Forchheimer medium is examined. The C-C heat flux, variable thermal conductivity, and mass diffusivity are all used to investigate heat transport. The flow originates from a source located at the intersection of the plates and constitutes the momentum conservation. The investigation includes entropy and Bejan analysis. The premises guide the mathematical modelling of the flow field. Through bvp4c techniques, numerical solutions are attained. Converging section velocity increases in response to increased porosity and the Forchheimer number. Variation in temperature is significant when classical heat flux is reverted. Higher thermophoretic and porosity parameters result in a higher rate of entropy formation, while the Darcy parameter promotes drastic increase. Bejan is an escalatingfunction ofBrownian and Darcy parameters, while the porosity parameter causes it to fall. Porosity and the Forchheimer number regulate skin friction.

Minimization of exergy destruction with discrete metal foam filling in a pipe under turbulent flow condition

PurposeThis study aims to present the numerical analysis of exergy transfer and irreversibility through the discrete filling of high-porosity aluminum metal foams inside the horizontal pipe.Design/methodology/approachIn this study, the heater is embedded on the pipe’s circumference and is assigned with known heat input. To enhance the heat transfer, metal foam of 10 pores per inch with porosity 0.95 is filled into the pipe. In filling, two kinds of arrangements are made, in the first arrangement, the metal foam is filled adjacent to the inner wall of the pipe [Model (1)–(3)], and in the second arrangement, the foam is located at the center of the pipe [Models (4)–(6)]. So, six different models are examined in this research for a fluid velocity ranging from 0.7 to7 m/s under turbulent flow conditions. Darcy Extended Forchheimer is combined with local thermal non-equilibrium models for forecasting the flow and heat transfer features via metal foams.FindingsThe numerical methodology implemented in this study is confirmed by comparing the outcomes with the experimental outcomes accessible in the literature and found a fairly good agreement between them. The application of the second law of thermodynamics via metal foams is the novelty of current investigation. The evaluation of thermodynamic performance includes the parameters such as mean exergy-based Nusselt number (Nue), rate of irreversibility, irreversibility distribution ratio (IDR), merit function (MF) and non-dimensional exergy destruction (I*). In all the phases, Models (1)–(3) exhibit better performance than Models (4)–(6).Practical implicationsThe present study helps to enhance the heat transfer performance with the introduction of metal foams and reveals the importance of available energy (exergy) in the system which helps in arriving at optimum design criteria for the thermal system.Originality/valueThe uniqueness of this study is to analyze the impact of discrete metal foam filling on exergy and irreversibility in a pipe under turbulent flow conditions.

Coercivity mechanism and long-range coupling of anisotropic Nd-Dy-Fe-Co-B/Fe composite thick film

In the present work, the long-range coupling between soft- and hard-magnetic layers and a dual enhancement of coercivity and polarization are achieved in anisotropic Nd-Dy-Fe-Co-B/Fe composite thick film with Ta spacer layers. It has been found that the coercivity mechanism dominated by the pinning mechanism is enhanced with increasing the periodic number of multilayers. The effect of the Ta spacer layer isolating the hard-magnetic phase grains leads to an increase in the coercivity. Continuous irreversible distribution confirms the coherent reversal of the soft and hard magnetic phases. The increase of polarization is caused by the dipole interactions acting in the long-range coupling between the layers.

Exergic performance of plate evaporator coated with nanoparticles for fish preservation

ABSTRACT A theoretical analysis is conducted using a nano-coated plate evaporator surface for fish preservation. Copper and alumina nanoparticles mixed with the base material (Steel) are considered for the evaporator material. Different brines (ethylene glycol, propylene glycol, potassium acetate, and calcium chloride) act as secondary refrigerants. Various performance parameters (pumping power, exergy rate change, irreversibility, exergic efficiency, non-dimensional exergy, and irreversibility distribution ratio) based assessment has been performed. The maximum percentage reduction in non-dimensional exergy and irreversibility, and maximum percentage rise in exergy rate change, irreversibility distribution ratio, and exergic efficiency have been acquired for propylene glycol brine. The pumping power decreased by 2.5% for alumina-copper hybrid nanoparticle-based material. The irreversibility and non-dimensional exergy have been reduced by 1.5%, whereas the exergy change rate, exergic efficiency, and irreversibility distribution ratio enhanced by 0.5%, 0.5%, and 2.5%, respectively, for PG brine (percentage-wise). The study reveals that the surface coated with nanoparticles provides better exergic performance.

Comparative study on four autocascade refrigeration cycles based on energy, exergy, economic and environmental (4E) analyses

As known, insufficient component separation of zeotropic refrigerant and massive throttling losses are two major causes for the poor performance of autocascade system. Aiming to combine the benefits of applying two-stage component separation to improve the component separation efficiency and applying ejector to recover partial expansion work, a novel ejector enhanced autocascade refrigeration cycle with two-stage component separation is proposed. The comparative study on the novel cycle and other three autocascade refrigeration cycles are conducted by simulation method, based on energy, exergy, economic and environmental analyses method. The simulation results show that the novel cycle always yields remarkable performance advantage. Under the given condition, the novel cycle respectively improves the coefficient of performance and cooling capacity by 40.8% and 60.8% compared with the convenient autocascade refrigeration cycle. Furthermore, the exergy performance and irreversibility distributions of four cycles are compared. Moreover, the performance variation of the novel cycle with main operation parameters is simulated to investigate the cycle characteristics. The novel cycle achieves the longest payback period of 2.27 years and produces the lowest full life cycle cost of 5268 $, when applied in a low-temperature freezer. Meanwhile, the novel cycle remarkably reduces the carbon dioxide and air pollution emissions.

Entropy generation analysis of turbulent flow in conical tubes with dimples: a numerical study

Minimizing the entropy generation rate is one of the key performance indicators for enhancing the thermal design of heat exchangers. This paper introduces a comprehensive numerical entropy generation analysis of turbulent water flow inside—newly proposed—conical tubes with dimples subjected to a constant heat flux. The effect of different tube diameter ratios (DR = 1, 1.5, 2, 3, and 5) and flow modes (convergent and divergent tube configurations) on the thermal, viscous, and total entropy generation rates is investigated within Reynolds number (Re) range of 3 × 103–40 × 103 using ANSYS-Fluent package. Realizable k-ε (RKE) turbulence model is adopted in this study. A well-validated 3D model was adopted to estimate the dimensionless indices: Bejan number (Be), enhanced entropy generation ratio (Ns,en), and the irreversibility distribution ratio ({phi }_{mathrm{s}}) to characterize the entropy generation performance and to compare conical dimpled tubes to smooth ones. The results showed that total entropy production rate values for dimpled tube geometries are lower than those for the corresponding smooth ones, especially for convergent dimpled tubes. Convergent dimpled tubes with DR in the range of 1.5–3 achieved the lowest total entropy production values over the whole Re range, with an average value of 0.20 W K−1, as compared to an average value of 0.34 W K−1 for the smooth configurations. The average Ns,en values for dimpled convergent tubes with DR = 1.5–3 are 0.46 and 0.80 at Re = 3000 and 40,000, with reductions of 50.54% and 3.61% at both Re values, respectively. The study also showed that the entropy generation analysis could provide an effective tool to highlight the optimal design of tube heat exchangers based on the minimum entropy generation and the enhanced entropy generation ratio.

Performance analysis on the parabolic trough solar receiver-reactor of methanol decomposition reaction under off-design conditions and during dynamic processes

Parabolic Trough Solar Receiver-Reactor (PTSRR) of Methanol Decomposition Reaction process (MDR), which can achieve chemical storage and efficient utilization of solar energy, has gained increasing attention recently. To comprehensively study the performance of PTSRR of MDR under off-design conditions and during dynamic processes, a model of PTSRR-MDR is developed and validated. Detailed energy and exergy analysis model are developed to figure out the irreversibility distribution. Results indicate that exergy destructions caused by solar concentrating and thermochemical reaction processes limit the improvement of exergy efficiency, which account 39.32% and 18.32%, respectively, under 800 DNI. When DNI step decreases from 800 to 400 W m−2, the methanol conversion rate decreases from 90.0% to 40.9% in ∼400 s. The solar-to-chemical exergy efficiency increases from 16.39% to 32.80% immediately, then decreases to the lowest value in 30 s, and rises to 11.23%. The efficiency is lower than the stable value transiently because the exergy stored in solid phase is partly destructed when converted to chemical exergy. Then, dynamic performance under DNI step increase is studied. Due to thermal inertia, additional chemical energy and exergy are gained or lost, compared to the ideal process. The results may provide some guidance for further efficient operation control.

Non-Darcy nanoliquid buoyant flow and entropy generation analysis in an inclined porous annulus: Effect of source-sink arrangement

In several engineering and industrial applications, the primary challenge in the design of thermal devices is to minimize the entropy production with maximum energy dissipation so that the system efficiency could be enhanced. In particular, an inclined partially heated annulus is far challenging due to the presence of both tangential and normal gravity components, which produces major impacts on the fluid movement and associated transport rates as well as entropy production. From several important applications point of view, the current investigation is mainly focused to address the combined impacts of source-sink arrangements as well as the annular inclination on buoyant nanoliquid motion, thermal dissipation along with irreversibility distribution in a tilted porous annulus. The governing model equations are numerically solved by utilizing the finite difference based time-splitting and relaxation techniques. Using second-order finite difference approximation, the partial derivatives are approximated and the resulting system of algebraic equations are inverted using Thomas algorithm. The influence of various controlling parameters such as geometric inclination angle, nanoparticle shape, Darcy number, length and position of source-sink on fluid movement, thermal and entropy distribution are scrutinized in detail. Through a wide range of numerical experiments, it has been found that the annular inclination angle and location of source-sink arrangement plays a vital role on fluidity and flow patterns of nanoliquid in the porous saturated annulus. For smaller size of source-sink pair, higher thermal dissipation with minimal entropy production could be achieved, which is an important observation for the design of thermally efficient systems. We have also noticed that a better thermal transport rate with minimum irreversibility rate could be attained for a particular source-sink arrangement, in particular for γ=0∘, the staggered positioning of source-sink pair is beneficial rather than in-line arrangement. Among the various parameters arising in this analysis, the nanoparticle shape has been one of the key parameters to test the thermal efficiency. It has been predicted that the blade shaped nanoparticle induces better thermal efficiency, among the five different shapes of nanoparticle. The outcomes of this analysis could be utilized in applications, such as solar systems, electronic equipment cooling and heat exchangers.

Process optimization and thermodynamic analysis of autothermal coal chemical looping gasification industrial demonstration system

Chemical looping gasification (CLG) is an innovative clean coal conversion technology with industrial application prospects. The technical reliability of coal CLG (CCLG) in an autothermal state remains to be investigated. To clarify the process characteristics of an autothermal CCLG process, a CCLG autothermal operation system was established based on a CLG industrial demonstration unit. Process modeling of the CCLG reactor system and economizer, air preheater, and other heat exchange units was performed, to ensure autothermal operation of the global CCLG process. The optimal operating parameters of the system were established, the optimal heat exchange network was designed, and the source and distribution of thermodynamic irreversibility were clarified. The results showed that the optimal coal feed flow rate, air feed temperature and flue gas circulation temperature were 437.07 kg/h, 550 °C and 450 °C, respectively. The fuel reactor (FR) flue gas circulation was not conducive to system autothermal, resulting in weakened gasification performance. The optimal heat exchange plan allowed the system to operate without an external heat source. The thermodynamic irreversibility mainly originated from the redox process. The system heat efficiency was 81.63 %, the product exergy efficiency was 78.06 %, the total exergy efficiency was 41.10 %, and the total exergy destruction rate was 55.40 %. Additionally, the FR flue gas circulation caused high exergy loss, resulting in reduced system thermodynamic efficiency.

Theoretical investigation and comparative analysis of the Linde–Hampson refrigeration system using eco-friendly zeotropic refrigerants based on R744/R1234ze(Z) for freezing process applications

The theoretical simulation and thermodynamic analyses of the Linde–Hampson refrigeration system using multiple eco-friendly zeotropic refrigerants are conducted to compare the optimal COP, volumetric refrigerating capacity and irreversibility distribution at the cold space temperature of -45 °C to -25 °C. The genetic algorithm is employed on the global optimization of Linde–Hampson refrigeration system to find out the optimal operating pressures and proportions of mixed refrigerants. By comparison, the most potential binary and ternary refrigerants are selected as R744/R1234ze(Z) and R744/R1234ze(E)/R1234ze(Z), respectively. The temperature glide of ternary refrigerant is mainly regulated by the proportions of the middle-boiling-point and high-boiling-point components. The temperature glide of zeotropic refrigerants should well match the temperature span between heat reservoirs, since the matching degree plays an essential role in system performance, and it can be regarded as an important basis for the selection of mixed refrigerants. The results of comparison with the R744 two-stage compression transcritical refrigeration system and the cascade refrigeration system using R744 and R1234yf show that the Linde–Hampson system using suitable mixed refrigerants can obtain the greatest COP and can be considered as a supplement and alternative. The research results will provide a reference to the applications of the Linde–Hampson refrigeration system using eco-friendly zeotropic refrigerants for freezing process in considerations of environmental protection, safety, and efficiency.